Screw

ABSTRACT

A fastener for securing remnant-producing materials, a method of manufacturing the fastener, and a method of using the fastener are provided. The fastener is configured such that in use any remnants or slivers produced by rotation of the fastener are forcibly driven into the surface of the material. In one aspect, the fastener has two separate threaded portions, a first or lower threaded portion and a second or upper threaded portion. The threads on the lower threaded portion have a pitch that is different from the threads on the upper threaded portion. In one embodiment, the lower threaded portion threads have a larger pitch than the threads on the upper threaded portion. In use, after the lower threaded portion is completely inserted into the material, the upper threaded portion of the fastener enters the material. Because the upper threaded portion has threads that have a pitch that is different from the threads on the lower threaded portion, the threads on the upper threaded portion capture the remnants that have been extruded within or onto the surface of the material. As the fastener is completely inserted into the material, the remnants that have been extruded by the lower threaded portion of the fastener are substantially retained in the bore by the upper threaded portion of the fastener.

BACKGROUND

The present invention relates generally to fastening systems. Inparticular, the present invention relates to a screw for penetrating andsecuring a workpiece.

In construction and furniture building involving wood products, the useof alternative materials is becoming more common. Some alternativematerials are made entirely from post-consumer polyethylene waste suchas bottles and other recycled plastics. Other alternative materials aremanufactured by mixing wood and other materials such as glass, steel,and carbon fibers with a suitable binder to vary the characteristics ofthe final material. Materials alternative to wood are used to constructeverything from cabinets to decks. Such alternative materials are madeby various processes. For example, alternative material lumber may bemade by blending recycled plastic resins with sawdust and extruding theblended mixture into standard lumber sections.

Such alternative materials have many advantages over wood. Thealternative materials are often stronger and more durable then evenpressure treated lumber. Many materials also offer better resistance tomoisture, corrosive substances, termites and other insects, and otherenvironmental strains that often prove to be detrimental to wood.

The use of standard fasteners with these alternative materials, however,may produce unwanted results. Screws are commonly used to affix oneworkpiece to another. However, some of the above mentioned alternativematerials may not compress as readily as wood to accommodate the addedvolume of the inserted screw. With respect to some of theabove-mentioned alternative materials, insertion of the screw,particularly if there is no pre-drilled hole to accommodate the screw,can cause remnants or shavings to be cut, extruded, or otherwise removedfrom the hole made by the screw. Such alternative materials may bereferred to as “remnant-producing” materials, and may include materialsin addition to the alternative materials mentioned above. Some of theremnants may remain attached to the material or held to the material bythe screw, and extend above the material surface. These remnants thenhave to be removed by sanding or other methods. A common way to reducethis problem is to pre-drill holes in the locations where a screw-typefastener must be inserted. This technique is laborious and timeconsuming. What is needed is a fastener adapted for use with aremnant-producing material where insertion of the fastener, particularlywithout pre-drilling holes, leaves a smoother surface on theremnant-producing material, reducing or eliminating remnants.

SUMMARY

The present inventions provide a fastener for securing remnant-producingmaterials, a method of manufacturing the fastener, and a method of usingthe fastener so that remnants or slivers produced by rotation of thefastener are substantially embedded within the remnant-producingmaterial.

A fastener is provided having two separate threaded portions, a first orlower threaded portion having a first thread pitch and a second or upperthreaded portion having a second thread pitch. The leading lower threadportion is designed to engage the work piece more firmly than thefollowing upper thread portion. Thus, upon insertion of the screw, asboth threaded portions engage the work piece, the first sectionsubstantially maintains its position or insertion rate with respect tothe work piece defined by the pitch of the lower threads. The secondthreaded portion having a different thread pitch engages the work pieceless firmly and thus is pulled through the work piece by the first setof threads substantially at the rate defined by the angle of the firstset of threads. If the respective upper and lower thread pitches wereequal, the upper threads would merely follow in the tracks or parallelto the tracks of the first leading threads. By making the thread pitchesdifferent, the second threaded portion engages and pulls with itremnants and/or wall material, retaining or pulling it into the bore.

In one aspect of the present inventions, the pitch of the second portionthreads is less than the pitch of the threads of the first portion. Thesecond threaded portion pitch in such an embodiment may spiral in thesame direction as the first thread portion, may be of zero pitch, i.e.,one or more rings around the screw shank, or may be of negative pitch,i.e., spiral in a direction that is opposite of the threads on the firstor lower threaded portion.

In another aspect of the present inventions, the threads on the secondor upper threaded portion have a larger diameter than the threads on thefirst or lower threaded portion.

In use, the first or lower threaded portion of the fastener is engagedwith the remnant-producing material and rotated in the direction of thethreads to insert the fastener into the material. This rotation mayproduce remnants or slivers by extruding, cutting, or some othermechanism. These remnants may extend from the hole in the material orworkpiece surface made by the screw.

After the lower threaded portion is completely inserted into thematerial, the upper threaded portion of the fastener enters thematerial. Because the upper threaded portion has threads that have adifferent thread pitch relative to the threads on the lower threadedportion, the threads on the upper threaded portion capture the remnantsthat have been extruded within and/or onto the surface of the workpiece.As the fastener is completely inserted into the material, the remnantsthat have been extruded by the lower threaded portion of the fastenerare substantially retained in the bore by the upper threaded portion ofthe fastener.

Therefore, a fastener and a method for inserting the fastener areprovided to answer a need that currently exists in the constructionindustry.

These and other features and advantages of the invention will be moreclearly understood from the following detailed description and drawingsof preferred embodiments of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a screw according to a preferred embodiment ofthe present invention.

FIG. 2 is a cross-sectional view showing the screw of FIG. 1 engaged ina remnant-producing material.

FIG. 3 is a view similar to FIG. 2.

FIG. 4 is a view similar to FIG. 2.

FIG. 5 is a side view of a screw according to another preferredembodiment of the present invention.

FIG. 6 is a view taken along section line VI-VI of FIG. 5.

FIG. 7 is a side view of a screw according to another preferredembodiment of the present invention.

FIG. 8 is a cross-sectional view showing the screw of FIG. 7 engaged ina remnant-producing material.

FIG. 9 is a view like FIG. 8.

FIG. 10 is a view like FIG. 8.

FIG. 11 is a view like FIG. 8.

FIG. 12 is a view like FIG. 8.

FIG. 13 is a view like FIG. 8.

FIG. 14 is a side view of a screw according to another preferredembodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Refer now to FIG. 1 there being shown a fastener or screw, generallydesignated by reference numeral 10, according to a preferred embodimentof the present invention. The fastener 10 includes a shank 20 extendingbetween a head 30 and a tapered tip 40. The head 30 has a diameter 32,and also includes a recess 34 (not shown) configured (e.g., slotted orcruciform shaped) to accommodate a driver for rotating the fastener 10.The screw 10 has an axis 25.

In the illustrated embodiment, the shank 20 of the fastener 10 has twothreaded portions: a first or lower threaded portion 50 and a second orupper threaded portion 60. In a preferred embodiment, the lower threadedportion 50 has right-hand threads 54. The upper threaded portion 60 hasleft-hand threads 64. The lower threaded portion 50 has a length 53, alower thread diameter 56, and a lower shank diameter 52. The upperthreaded portion 60 has a length 63, an upper thread diameter 66, and anupper shank diameter 62.

The threads on the first or lower threaded portion 50 have a pitch 58that is defined by the axial distance from a point (usually the crest)on a thread to a corresponding point on an adjacent thread. The threadson the second or upper threaded portion 60 have a pitch 68 that issimilarly defined. In the illustrated embodiment, the thread pitch 68 ofthe upper threaded portion 60 is negative and thus is less than thethread pitch 58 of the lower threaded portion 50.

The head diameter 32 is greater than the shank diameters 52 and 62. Asillustrated in FIG. 1, a neck 70 extends between the upper threadedportion 60 and the head 30. The neck 70 has an outer surface 72. In theillustrated embodiment, the neck 70 is manufactured to have a diameterenlarging in a tapered fashion to transition from the upper threadedportion shank diameter 62 to the head diameter 32. In the illustratedembodiment, the lower part of the neck 70 has the same diameter as theshank diameter 62, and the upper part of the neck 70 is the same indiameter as the head diameter 32. In this embodiment, the neck 70 ismanufactured to be of increasing diameter from the lower portion to theupper portion of the neck 70. The neck surface 72 is tapered from theshank diameter 62 to the head diameter 32. Alternatively, a portion orportions of the neck could be straight or not tapered. The neck istapered so that in use, as the leading surface, i.e., the neck surface72 of the illustrated embodiment, enters a work piece, the work piecewill gradually compress to accommodate the screw 10 as it is inserted,preferably without the need to pre-drill holes in the work piece. Thedesirable angle or degree of taper may depend upon the compressibilityor the characteristic of the work piece. Any abrupt flange, protrusion,ridge or other surface in the leading neck surface 72 could engage thework piece and inhibit the screw's insertion into the work piece,particularly if the abrupt surface has to travel a substantial distanceinto the material.

The upper threaded portion 60 and the lower threaded portion 50 areseparated by a transition section 24 that has a length 26. Thetransition section 24 is manufactured to contain no threads. In theillustrated embodiment, the transition section 24 has a diameter 22 thatis slightly greater than the shank diameters 52 and 62, but smaller thanthe upper and lower thread diameters 66 and 56. Alternatively, thetransition section diameter 22 can be equal to or smaller than the shankdiameters 52 or 62, but should not be so large as to substantiallyinhibit insertion of the screw into the work piece. For example, powderymaterial, such as drywall, easily breaks or compresses, and couldaccommodate abrupt changes or flanges, whether or not the materialproduces remnants from any paper or other coverings. However, othermaterials are more resistant to compression and tapered neck screw headsare more readily insertable into such materials.

The lower threaded portion 50 extends to the tapered tip 40 and a point28, similar to a conventional wood screw. The point 28 is essentially asharp end to the shank 20. As illustrated in FIG. 1, the tapered tip 40is manufactured to be decreasing in diameter from the shank diameter 52to the point 28. The threads 54 of the lower threaded portion 50 areconventionally manufactured to continue onto the tapered tip 40 and toend at the point 28. The lower threaded portion thread diameter 56decreases at the tapered tip 40 and comes to an essentially sharp end onpoint 28. The lower threaded portion threads 54 on the tapered tip 40and point 28 may be manufactured to be self-tapping threads.Self-tapping threads reduce the need to pre-drill holes in a workpiece.

The fastener 10 is manufactured from a blank that may initially beuniform in diameter. The blank, which may be made form steel, aluminum,or other material, is deformed by a thread rolling machine to achievethe form illustrated in FIG. 1. The blank may be rolled in a firstdirection to form the first or lower threaded portion 50. The blank maybe rolled in a second direction to form the second or upper threadedportion 60. The head 30, the neck 70, and the tapered section 22 may beformed during the above mentioned rolling steps, or during separaterolling steps. Alternatively, the rolling machine may have appropriatedies so that the fastener 10 can be manufactured in one rolling step.During the rolling process, threads may receive forging properties thathelp increase the fastener's fatigue strength and loading strength.

Refer now to FIG. 2 that illustrates the fastener 10, aremnant-producing material 82, a base material 84, and remnants 80. Inuse, as the fastener 10 is rotated into the remnant-producing material82, remnants are cut, extruded, or otherwise removed to the surface 83of the remnant-producing material 82. The remnants 80 are forced out ofthe remnant-producing material 82 by the rotation of the threads 54 onthe lower threaded portion 50 of the fastener 10.

Refer now to FIG. 3 that illustrates the fastener 10, theremnant-producing material 82, the base material 84, and remnants 80. Inuse, at this stage of the method of the present invention the lowerthreaded portion 50 and the transition section 24 are completelyinserted into the remnant-producing material 82. The lower threadedportion 50 may also at this stage become engaged with the base material84. The upper threaded portion 60 is at this stage at least partiallyinserted into the remnant-producing material 82. The upper threadedportion 60, by virtue of having threads 64 with a different pitch fromthe lower portion 50, captures the remnants 80 onto the upper threadedportion 60. The remnants 80 are captured by the threads 64 of the upperthreaded portion 60 and may also be captured by the neck 70. As thefastener 10 is further inserted into the remnant-producing material 82,the remnants 80 are forcibly driven from the surface 83 of theremnant-producing material 82 and from the upper threaded portion 60into the hole or bore 87 of the remnant-producing material 82 along withthe fastener 10.

Refer now to FIG. 4 that illustrates the screw 10, the remnant-producingmaterial 82, the base material 84, and the remnants 80. In use, at thisstage of the method of the present invention the fastener 10 iscompletely inserted into the remnant-producing material 82. Remnants 80that have been cut, extruded, or otherwise removed from theremnant-producing material 82, as illustrated in FIGS. 1 and 2, havebeen forcibly driven into the remnant-producing material 82 by the upperthreaded portion 60, neck 70, and head 30. Remnants 80 are below head30, thus leaving a smooth surface 83 on the remnant-producing material82.

As is shown in FIG. 4, the screw 10 is utilized to clamp theremnant-producing material 82 to the base material 84. A common problemexperienced when attempting to clamp one structure to another with ascrew having threaded sections with a constant thread pitch isdifficulty in tightly clamping, or seating, the two structures againstone another. This is in part a result of a broaching effect stemmingfrom the threaded section closest to the screw head, which leads tojacking, or the tendency for structures to remain separated. To ensuretighter seating of the two structures, a differential should be presentbetween the threaded sections. Conventionally, a differential isapproximated by pre-drilling the upper structure.

As shown in FIG. 4, the lower threaded portion 50 has a thread pitchwhich differs from the thread pitch of the upper threaded portion 60.This differential, coupled with the ability of the upper threadedportion 60 to pull the remnants 80 into, and thereby clean, the bore 87,suppresses jacking and allows a tight clamp between theremnant-producing material 82 and the base material 84. Consequently, anadditional step of pre-drilling the remnant-producing material 82 isobviated.

To ensure proper clamping between the remnant-producing material 82 andthe base material 84, preferably the uppermost extent of the lowerthreaded portion 50 should be fully within the base material 84 andclose to the mating surfaces of the materials 82, 84 when the head 30 ofthe screw 10 is seated within the remnant-producing material 82. Sincethe uppermost extent of the lower threaded portion 50 should be near tothe mating surfaces of the materials 82, 84, properly sized andconfigured screws 10 should be chosen based upon the relativethicknesses of the materials 82, 84.

Refer now to FIGS. 5 and 6 that show a screw, generally designated byreference numeral 110, according to another embodiment of the presentinvention. The fastener 110 has a head 130 that has a diameter 132. Thefastener 110 has a neck 170 that has a lower neck portion 174 and anupper neck portion 172. The upper neck portion 172 and the lower neckportion 174 are separated by a land surface 190. The land surface 190has an inside diameter 178 and an outside diameter 176.

As shown in FIG. 6, the lower neck portion 174 and the upper neckportion 172, as well as the neck 170 overall, have substantially taperedleading surfaces. Although the neck 170 has the land surface 190, nosubstantial abrupt leading surfaces or protrusions exist from the lowerneck portion 174 to the head 130 as the neck 170 diameter increases,ultimately becoming the same in diameter as head diameter 132. In use,the substantially tapered leading surface of the lower neck portion 174and an upper neck portion 172 can be inserted into a workpiece so thatno substantial abrupt surface or protrusion enters the workpiece in aleading fashion, i.e. faces the workpiece in the direction of entry.Because the land surface 190 is not a leading surface, its abrupt natureshould not substantially inhibit insertion of the screw into theworkpiece. In the preferred embodiment of the neck illustrated in FIGS.5 and 6, the remnants 80 that are cut or extruded from theremnant-producing material 82 may also be captured by the lower neckportion 174, the upper neck portion 172, and the land area 190.

Refer now to FIG. 7 there being shown a screw, generally designated byreference numeral 200, according to another embodiment of the presentinvention. The screw 200 has a first or lower threaded portion 250 thathas threads 254. The threads 254 have a thread pitch 258 and a threaddiameter 256. The screw 200 has a second or upper threaded portion 260that has threads 264. The threads 264 have a thread pitch 268 and athread diameter 266.

In this embodiment of the present invention, the lower threaded portionthreads 254 and the upper threaded portion threads 264 spiral the samedirection. Preferably, the threads 254 and 264 are right-hand threads,however, the threads 254 and 264 may be left-hand threads. In theillustrated embodiment, the lower threaded portion thread pitch 258 isgreater than the upper threaded portion thread pitch 268. Preferably,the lower threaded portion thread diameter 256 is smaller than the upperportion thread diameter 266. Also preferably the lower threaded portionthread angle 251 is greater than the upper portion thread angle 261,because it is desired that the upper threads will grasp and pullmaterial down the bore rather than extrude a new thread pattern in thebore.

The screw 200 has a transition section 224 that has no threads. Thetransition section provides an annulus between it and the inside surfaceof the bore for accepting remnant and bore material being drawn throughthe bore and may be selected to reside proximate the intersection of thetwo pieces being fastened together to thus aid in drawing those piecestogether. Alternatively, no transition zone may be used. As is notedwith reference to the threaded portions 50, 60 shown in FIG. 4, thethread pitch of the lower and upper threaded portions 250, 260 aredifferent, and that difference suppresses jacking and enhances tightclamping between the remnant-producing material 82 and the base material84.

A benefit of this embodiment is that the remnant-producing material 82is urged toward the base material 84 if there is a gap between the twomaterials 82 and 84 at the time the screw 200 is inserted. Because thelower threaded portion thread pitch 258 is greater than the upperthreaded portion thread pitch 268, the lower threaded portion 250 willtravel at a quicker axial rate through a material than will the upperthreaded portion 260. In use, with reference to FIG. 8, there may be agap 85 between the remnant-producing material 82 and the base material84 when the screw 200 engages the base material 84. With reference toFIGS. 9 and 10, the lower threaded portion 250 will travel at a quickeraxial rate through the base material 84 relative to the axial travelrate of the upper threaded portion 260 through the remnant-producingmaterial 82. Therefore, the remnant-producing material 82 will be urgedtoward the base material 84. Also shown in FIG. 10 are the annulus 89which provides space for accepting bore material and remnants, and thebore 87 made by the threads 264. Finally, it should be noted that theuppermost extent of the lower threaded portion 250 is fully within thebase material 84 and near to the mating surfaces of the materials 82, 84when the head of the screw 200 is seated within the remnant-producingmaterial 82. While it is possible for a portion of the upper threadedportion 260 to extend into the base material 84, as shown in FIG. 10 allof the upper threaded portion 260 is resident within theremnant-producing material 82. Preferably, since the uppermost extent ofthe lower threaded portion 250 should be near to the mating surfaces ofthe materials 82, 84, properly sized and configured screws 200 should bechosen based upon the relative thicknesses of the materials 82, 84.

Refer now to FIGS. 11, 12, and 13, that illustrate how the screw 200captures the remnants that have been extruded onto the surface of theremnant-producing material. In use, remnants 80 that are shaved, cut, orotherwise pushed to the surface 83 of the remnant-producing material 82are captured by the threads 264 of the upper threaded portion 260.Because the upper threaded portion thread pitch 268 is smaller than thelower thread pitch 258, the upper threads 264 are able to capture theremnants 80. Additionally, because the upper thread pitch 268 is smallerthan the lower thread pitch 258, the upper threads 264 deform the pathcut in the remnant producing material 82 by the lower threads 254.Alternatively, the above mentioned useful task can be accomplished ifthe upper portion thread diameter 266 is greater than the lower portionthread diameter 256. When the screw 200 is fully inserted, the remnants82 are forcibly driven into the remnant-producing material 82. Refer nowto FIG. 14 that shows a screw, generally designated by reference numeral300, according to another embodiment of the present invention. The screw300 has a lower threaded portion 350 having threads 354 that a threaddiameter 356. Instead of an upper threaded portion, the screw 300 has anupper annular ridge section 398 (spaced threads with zero pitch) thathas annular ridges 390. The annular ridges have a ridge diameter 366 anda ridge height 392. Preferably, the ridge diameter 366 is greater thanthe lower thread diameter 356. The ridge diameter 366 may be equal to orsmaller than the lower thread diameter 356. The annular ridge section398 has a length 363 that may be smaller, equal to, or greater than thelower portion thread length 353. The annular ridges 390 havehorizontally flat surface 396 and an angled surface 394. On the screw300, the annular ridge flat surface is facing the tapered tip 340, andthe annular ridge angled surface 394 faces the head 330.

The above description and drawings are only illustrative of preferredembodiments of the present inventions, and are not intended to limit thepresent inventions thereto. Any subject matter or modification thereofwhich comes within the spirit and scope of the following claims is to beconsidered part of the present inventions.

1. A screw comprising: a shank having a head end and a point end; saidshank having a first threaded section and a second threaded section,said first threaded section being closer to said point end than saidsecond threaded section; said first threaded section having threads thathave a first pitch, said second threaded section having threads thathave a second pitch, different from said first pitch; said firstthreaded section having a first thread diameter, said second threadedsection having a second thread diameter larger than said first threaddiameter, and said head having a third diameter, said third diameterbeing greater than said first and second diameters; and said firstthreaded section having a first thread angle, said second threadedsection having a second thread angle smaller than said first threadangle. 2-13. (canceled)